Highly Efficient (>9%) Lead‐Free AgBiS₂ Colloidal Nanocrystal/Organic Hybrid Solar Cells

Abstract

Environmentally friendly colloidal nanocrystals (NCs) are promising materials for next‐generation solar cells because of their low cost, solution processability, and facile bandgap tunability. Recently, silver bismuth disulfide (AgBiS2) has attracted considerable attention owing to its appreciable power conversion efficiency (PCE) of 6.4%. However, issues such as the low open‐circuit voltage (VOC) compared to the bandgap of the AgBiS2 NCs and the unoptimized energy level structure at the AgBiS2 NC/PTB7 hole‐transporting layer (HTL) interface should be resolved to enhance the performance of solar cells. In this study, a design strategy to obtain efficient energy level structure in AgBiS2 NC/organic hybrid solar cells is proposed. By selecting PBDB‐T‐2F as an HTL with a lower highest occupied molecular orbital level than that of PTB7, the VOC of the device is increased. Furthermore, iodide‐ and thiolate‐passivated AgBiS2 NC surfaces are generated using tetramethylammonium iodide (TMAI) and 2‐mercaptoethanol (2‐ME), which leads to the energy level optimization of NCs for efficient charge extraction. This improves the PCE from 3.3% to 7.1%. In addition, the polymer is replaced with a PBDB‐T‐2F:BTP‐4Cl blend to achieve a higher short‐circuit current density through complementary absorption. Accordingly, an AgBiS2 NC‐based solar cell with a PCE of 9.1% is fabricated.

Toward efficient hybrid solar cells comprising quantum dots and organic materials: progress, strategies, and perspectives

“…The group further developed AgBiS 2 QD inks with 3-mercaptopropionic ligands, which can process with environment-friendly water, resulting in a PCE of 7.3% with a PTAA interface layer. 56 A recent work by Lee's group revealed that the performance of the AgBiS 2 QD/organic hybrid solar cells can be also enhanced by introducing PM6:BTP-4Cl blend. They employed the commonly used ligands, tetramethylammonium iodide and 2-mercaptoethanol, to provide the great passivation of AgBiS 2 QDs, which could deliver a high PCE of ∼9.1% (Fig.…”

“…Recently, AgBiS 2 QD solar cells have made a breakthrough in photovoltaic performance from ∼6.0% to over 9.0% with great passivation and the matched organic semiconductors. 56,59 Nevertheless, the performance still lags far behind those of PbS and perovskite QD counterparts, mainly stemming from high energy loss. More efforts should be devoted to improving the passivation of AgBiS 2 QDs and developing favorable organic HTLs.…”

“…The star nontoxic AgBiS 2 QDs have seen a dramatic surge due to their promising opto-electronic properties, including broad absorption range, high absorption coefficient, favorable energy landscape, and great ambient stability. [54][55][56][57] With joint efforts, the photovoltaic performance of AgBiS 2 QDSCs has been improved to over 9.0% in 2022 (Fig. 1b).…”

Novel Ag-based thin film solar cells: concept, materials, and challenges

“…In addition, by adopting PBDB-T-2F:BTP-4Cl as a hole transport layer to obtain high J sc , the AgBiS 2 power conversion efficiency reaches 9.1%. 57 Since 2013, researchers have improved the device efficiency by adjusting the preparation process of AgBiS 2 NCs and optimizing the device structure. According to our review of the literature, AgBiS 2 thin film solar cells prepared by the SILAR method are one of the most effective devices with a breakthrough efficiency since no ligand exchange is involved.…”

“…In addition, by adopting PBDB-T-2F:BTP-4Cl as a hole transport layer to obtain high J sc , the AgBiS 2 power conversion efficiency reaches 9.1%. 57…”