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Monolithic perovskite–silicon tandem solar cells with MoOx hole selective contact silicon bottom solar cells show a power conversion efficiency of 8%. A thin 15 nm-thick MoOx contact to n-type Si was used instead of a standard p+ emitter to collect holes and the SiOx/n+ poly-Si structure was deposited on the other side of the device for direct tunneling of electrons and this silicon bottom cell structure shows ~15% of power conversion efficiency. With this bottom carrier selective silicon cell, tin oxide, and subsequent perovskite structure were deposited to fabricate monolithic tandem solar cells. Monolithic tandem structure without ITO interlayer was also compared to confirm the role of MoOx in tandem cells and this tandem structure shows the power conversion efficiency of 3.3%. This research has confirmed that the MoOx layer simultaneously acts as a passivation layer and a hole collecting layer in this tandem structure.

Lately, carbazole‐based self‐assembled monolayers (SAMs) are widely employed as effective hole‐selective layers (HSLs) in inverted perovskite solar cells (PSCs). Nevertheless, these SAMs tend to aggregate in solvents due to their amphiphilic nature, hindering the formation of a monolayer on the ITO substrate and impeding effective passivation of deep defects in the perovskites. In this study, a series of new SAMs including DPA‐B‐PY, CBZ‐B‐PY, POZ‐B‐PY, POZ‐PY, POZ‐T‐PY, and POZ‐BT‐PY are synthesized, which are employed as interfacial repairers and coated atop CNph SAM to form a robust CNph SAM@pseudo‐planar monolayer as HSL in efficient inverted PSCs. The CNph SAM@pseudo‐planar monolayer strategy enables a well‐aligned interface with perovskites, synergistically promoting perovskite crystal growth, improving charge extraction/transport, and minimizing nonradiative interfacial recombination loss. As a result, the POZ‐BT‐PY‐modified PSC realizes an impressively enhanced solar efficiency of up to 24.45% together with a fill factor of 82.63%. Furthermore, a wide bandgap PSC achieving over 19% efficiency. Upon treatment with the CNph SAM@pseudo‐planar monolayer, also demonstrates a non‐fullerene organic photovoltaics (OPVs) based on the PM6:BTP‐eC9 blend, which achieves an efficiency of 17.07%. Importantly, these modified PSCs and OPVs all show remarkably improved stability under various testing conditions compared to their control counterparts. A new series of SAMs from DPA‐B‐PY to POZ‐BT‐PY, employed as interfacial repairers, are coated atop CNph SAM to form a robust CNph SAM@pseudo‐planar monolayer as HSL in inverted PSCs. The CNph SAM@pseudo‐planar monolayer strategy enables a well‐aligned interface with perovskites, synergistically promoting perovskite crystal growth, improving charge extraction/transport, and minimizing nonradiative interfacial recombination loss.

To effectively minimize reflection losses and achieve compatibility with industrial‐scale silicon production lines, textured silicon/perovskite tandem solar cells have garnered significant attention in recent research. However, achieving uniform and stable coverage of the textured silicon substrate with hole‐selective layer (HSL) remains a significant challenge. Herein, a HSL material, DPAICz ((indolo[2,3‐a]carbazole‐11,12‐diylbis(ethane‐2,1‐diyl))bis(phosphonic acid)), is reported specifically designed for textured silicon substrate. Compared to the typical HSL material 2PACz, DPAICz features a π‐expanded conjugated core and multiple anchoring groups, forming a split‐standing configuration with anchoring groups positioned on opposite sides, resulting in superior anchoring stability on textured substrate under external stimuli. Moreover, DPAICz exhibited a larger molecular dipole moment and a more pronounced p‐type characteristic, enhancing the interfacial hole extraction efficiency. Consequently, wide‐bandgap (1.68 eV) perovskite solar cells employing DPAICz as the HSL achieved a champion power conversion efficiency (PCE) of 23.42%. Introducing the DPAICz into monolithic silicon/perovskite tandem solar cells greatly improved their performance, achieving a remarkable PCE of 32.55% in 1 cm2 area. Importantly, the unencapsulated tandems based on DPAICz exhibited significantly enhanced long‐term operational stability, retaining 96% of its initial PCE after 880 h of continuous 1‐sun light soaking at 45 °C under open‐circuit condition. An indolocarbazole‐based HSL material (DPAICz) with a split‐standing molecular configuration is reported specifically designed for textured silicon substrates. Due to its strong anchoring stability and excellent hole extraction efficiency, monolithic textured silicon/perovskite tandem solar cells employing DPAICz as the HSL achieved a remarkable power conversion efficiency of 32.55% in 1 cm2 area, along with significantly enhanced long‐term operational stability.

The interface between nickel oxide (NiOx) and self-assembled monolayers (SAMs) in perovskite solar cells (PSCs) often suffers from limited adsorption strength, poor energy-level alignment, and inadequate defect passivation, which hinder device performance and stability. To address these issues, we introduce a hybrid hole selective layer (HSL) combining atomic layer deposition (ALD)-fabricated NiOx with full-aromatic SAM molecules, creating a highly stable and efficient interface. ALD NiOx, enriched with hydroxyl groups, provides robust adsorption sites for the SAM molecule MeO-PhPACz, ensuring a strong, stable interaction. This hybrid HSL enhances energy-level alignment, hole selectivity, and defect passivation at the NiOx/perovskite interface. Devices utilizing this approach demonstrate significant performance improvements, achieving a power conversion efficiency (PCE) of 21.74%, with reduced voltage losses and minimal hysteresis. Furthermore, operational stability tests reveal enhanced durability under elevated humidity and temperature conditions. These findings highlight the potential of ALD NiOx and SAM hybrid HSL to overcome existing barriers, advancing the commercial viability of PSC technologies.

Carrier selective contact (CSC) architecture is one of several promising candidates for high-efficiency silicon solar cells operating close to the thermodynamic limit. However, an industrially feasible process is lacking for manufacturable CSC cells. Specifically, although evaporated molybdenum oxide (MoOx) has been actively researched as a hole selective layer, a more industry-compatible deposition process is critically needed. Atomic layer deposition (ALD) has been widely employed in the industry for material stacks requiring precise thickness control and uniformity. In this paper, we present a performance analysis of CSC solar cells fabricated using ALD MoOx as the hole selective layer. As a first step, the standard ALD recipe was modified to obtain sub-stoichiometric MoOx with a higher work function due to increased oxygen vacancy concentration. The modified MoOx recipe resulted in low open-circuit voltage values in fabricated not-passivated CSC solar cells. A 4 nm thick amorphous silicon layer inserted in the hole selective stack showed significant improvement in minority lifetime but worse solar cell performance due to increased series resistance. Besides indicating a strong trade-off between passivation and series resistance, the solar cell data highlights series resistance as a key performance limiter in CSC solar cells.

With the advancement of technology, inexpensive and highly scalable deposition techniques are extremely desirable for low-cost device fabrication. Aerosol-assisted chemical vapor deposition (AACVD) is a less complex and scalable deposition technique that works at atmospheric pressure. In this article, we demonstrate the growth of chromium oxide (Cr 2 O 3 ) films onto n-type silicon substrates utilizing the AACVD method, leading to the first-ever p-Cr 2 O 3 /n-silicon heterojunction device by this method. In this paper, we have analyzed the effect of temperature and concentration of precursor solution on the morphology of the deposited films. The structural analysis of the Cr 2 O 3 films shows a closely packed uniform structure with the root mean square (RMS) value of surface roughness varying from 1.6 nm to 5.99 nm. The maximum growth rate of 45.20 nm/min on silicon substrate was observed at 500 °C with 0.05 M precursor solution. X-ray photoelectron spectroscopy (XPS) showed a mixed phase layer, with the ratio of Cr 3+ to Cr 6+ for the film deposited at 450 °C, with 0.05 M precursor solution being 1.51 and increasing with the deposition temperature. The current–voltage characteristics showed a diode-like behavior with a high cut-in voltage of about 2 V. A high cut-in voltage exists due to a significant band offset at both the conduction band and valence band exists between Cr 2 O 3 and silicon. The utilization of the AACVD technique to grow Cr 2 O 3 on silicon substrate using chromium acetylacetonate as a precursor combined with the illustration of diode characteristics provide the novelty of this work.

This chapter contains sections titled: Introduction Conventional Structure Inverted Structure Tandem Structure Additional Oxides (Cr 2 O 3 , CuO x , PbO) Conclusions

This chapter contains sections titled: Introduction Electrolytes Transition Metal Oxides (TMOs) Organic Semiconductors Outlook Acknowledgement

Conventional diffusion process to form the emitter of a c-Si solar cell is a complicated process with high thermal as well as economic budget. An alternative to avoid this process is to form MIS/SIS structured solar cells, where different process is used to form the emitter portion of the cell. In this study, 3 × 3 (ITO-Al2O3-n-Si) structured SIS cell is developed, where n-Si is the base material, Al2O3 and ITO layer act as hole selective layer and emitter layer, respectively. Sputtered ITO layer of thickness 150 nm acts as a degenerative semiconductor as well as ARC. For ITO coated cell, average reflectance reduced to 4.54 % from 13.63% compared with only textured cell. Metallization is done using Ag on both the sides on the front side above the ITO layer and a continuous contact on the back side by vacuum coating unit. Apart from hole tunnelling, ALD grown very thin 1.5 nm layer of Al2O3 acts as a passivation layer and increases minority carrier lifetime from 9.732 S to 17.548 S. Achieved open circuit voltage (Voc) and short circuit current (Isc) are 684 mV and 35 mA, respectively.