Redefining PbS quantum dot photovoltaics: p-i-n devices with superior efficiency and reproducibility

Developing diverse photovoltaic device architectures is essential not only for improving power conversion efficiency (PCE) but also for enabling seamless integration with other photovoltaic materials in high-performance tandem configurations. While n-i-p architectures have historically dominated the development of PbS colloidal quantum dots (CQDs) solar cells, p-i-n counterparts have significantly lagged behind in efficiency, limiting their potential for further advancement. In this work, the advantage of the surface tunability of CQDs is taken by anchoring the classical self-assembled monolayer (SAM) molecule MeO-2PACz onto PbS CQDs via ligand exchange, forming a PbS-SAM bridging-layer, which is inserted between NiOx/SAM and the CQD active layer, resulting in a NiOx/SAM/PbS-SAM composite hole transporting layer (HTL). This structure effectively passivates the buried interfacial traps and enhances hole extraction. As a result, a record PCE approaching 14% is achieved, with a certified value of 13.62%, which is not only largely surpassing the previous highest value of 9.70% for p-i-n PbS QD solar cells, but also exceeds the current PCE record set by n-i-p architectures. Moreover, the p-i-n configuration exhibits excellent reproducibility, providing a robust and scalable platform for future applications, particularly as a narrow-bandgap subcell in monolithic tandem devices with wide-bandgap materials such as perovskites.