Green AgBiSe2/AgBiS2 core shell quantum dots for stable solar cells by robust SILAR method

Silver bismuth sulphide (AgBiS 2 ) ternary quantum dots are emerging as benign photon absorbers for solar cells. Higher absorption coefficient, easy processability and favourable bandgaps have enabled their potential use in solar cells. In this work, for the first time an in-situ (SILAR - Successive ionic layer adsorption and reaction) water protocol is designed for a stable solar cell device using type-I heterostructure of AgBiSe 2 /AgBiS 2 core shell quantum dots. The cells are fabricated by SILAR method unlike many reports of pre-synthesized quantum dots (QDs) making the device protocol highly robust. Alongside, various low-cost inorganic and solid-state hole transport materials are investigated for eliminating the woes of liquid electrolyte for this device. IV analysis carried out for the device performance reveals the designed heterostructure enhances the power conversion efficiency up to 70% (2.1%) from single junction AgBiS 2 (1.4%) device. AgBiS 2 acts as an absorber and also allows the confinement of electrons and holes in the core of AgBiSe 2 . AgBiS 2 thus acts as passivating layer for the core, reducing free charge carriers from reaching the trap states located at particle surface. Type-I AgBiSe 2 /AgBiS 2 core shell QDs show least recombination of excited electrons , better stability and higher quantum yield showing potential towards other photo applications like labelling and LEDs. • Effective improvisation of charge extraction and reduced recombination losses. • Designed a novel in-situ SILAR water protocol for robust, low cost solar cells. • Explored AgBiSe 2 /AgBiS 2 QD-heterostructure as efficient solar cell absorbers. • The core-shell heterostructure enhanced the overall P.C.E of the solar cell by 50%. • Shell passivates the core, and core confines the charge carriers, thus avoiding their recombination.