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Ultrathin solar cells can be a path forward to low‐cost photovoltaics due to their reduced material consumption and shorter required deposition times. With excellent surface passivation, such devices may feature higher open‐circuit voltages (VOC). However, their short‐circuit current density (JSC) may be reduced due to decreased light absorption. This mandates implementation of efficient light‐trapping structures. To design efficient ultrathin solar cells that combine surface‐passivation and light‐trapping features, accurate 3‐D modeling is necessary. To this end, a novel 3‐D optoelectrical finite‐element model is developed to analyze the performance of ultrathin solar cells. The model is applied to the case of ultrathin (<500 nm) chalcogenide solar cells (copper indium gallium (di) selenide, CIGSe), rear‐passivated with nanostructured Al2O3 to circumvent optical and electrical losses. It is found that such a nanopatterned dielectric passivation scheme enhances broadband light‐trapping with reduced rear‐surface recombination, resulting in an absolute power conversion efficiency enhancement of 3.9%, compared to cells without passivation structure. Overall, the work shows how 3‐D finite element modeling can aid in analyzing and developing new optical and electrical solar cell designs for ultrathin solar cells such as those based on chalcogenides and perovskites. [ABSTRACT FROM AUTHOR]

Sputtered nickel oxide (NiOx) is an attractive hole‐transport layer for efficient, stable, and large‐area p‐i‐n metal‐halide perovskite solar cells (PSCs). However, surface traps and undesirable chemical reactions at the NiOx/perovskite interface are limiting the performance of NiOx‐based PSCs. To address these issues simultaneously, an efficient NiOx/perovskite interface passivation strategy by using an organometallic dye molecule (N719) is reported. This molecule concurrently passivates NiOx and perovskite surface traps, and facilitates charge transport. Consequently, the power conversion efficiency (PCE) of single‐junction p‐i‐n PSCs increases from 17.3% to 20.4% (the highest reported value for sputtered‐NiOx based PSCs). Notably, the N719 molecule self‐anchors and conformally covers NiOx films deposited on complex surfaces. This enables highly efficient textured monolithic p‐i‐n perovskite/silicon tandem solar cells, reaching PCEs up to 26.2% (23.5% without dye passivation) with a high processing yield. The N719 layer also forms a barrier that prevents undesirable chemical reactions at the NiOx/perovskite interface, significantly improving device stability. These findings provide critical insights for improved passivation of the NiOx/perovskite interface, and the fabrication of highly efficient, robust, and large‐area perovskite‐based optoelectronic devices. [ABSTRACT FROM AUTHOR]