Quantum Dot/Polymer Bulk Heterostructure Interlayer for Enhanced Charge Collection in AgBiS2 Quantum Dot Photovoltaics

Remarkable progress over the past decade in photovoltaics using solution‐processed nanomaterials as light absorbers has placed colloidal quantum dot (CQD)‐based devices on the map. As such, AgBiS2 CQDs have garnered significant attention as materials exhibiting a high absorptivity with environmentally benign alternatives to Pb‐chalcogenide or Pb halide perovskite‐CQDs. Yet, AgBiS2 CQD‐based solar cells have gravely underperformed compared to Pb‐containing devices, particularly in the metrics of charge carrier extraction from the AgBiS2 absorber, hence its relative mediocrity. To specifically address the extraction efficiency, a bulk heterostructure (QPB) interlayer at the CQD/polymer interface in AgBiS2 CQD solar cells, resulting in an increase of the power conversion efficiency (PCE), e.g., from 5.10% (an average PCE of 4.94 ± 0.11%) to 6.78% (an average PCE of 6.59 ± 0.11%) is deviced. The improved charge extraction at the hole‐collecting interface is responsible for the superior performance, corroborated by high photocurrent (21.5 mA cm–2) and fill factor (67%). The QPB‐interlayered solar cell also gives rise to outstanding durability of the devices, retaining above 95% of the original PCE for 5 months in ambient air. Our strategy based on an eco‐friendly CQD/polymer could provide an effective route for next‐generation optoelectronics with enhanced charge collection and durability. Quantum dot/polymer bulk heterojunction (QPB) film composed of a blend of AgBiS2 colloidal quantum dots (CQDs) and PTB7 is devised as an interlayer in the AgBiS2 CQD solar cell leading to high‐efficiency, stable devices under ambient air. The best‐performing QPB device shows a power conversion efficiency of 6.8% (control device: 5.1%) with retaining its original efficiency over 95% over 5 months in ambient air.