All-inorganic quantum dot assisted enhanced charge extraction across the interfaces of bulk organo-halide perovskites for efficient and stable pin-hole free perovskite solar cells

Dibyendu Ghosh; Dhirendra K Chaudhary; Md Yusuf Ali; Kamlesh Kumar Chauhan; Sayan Prodhan; Sayantan Bhattacharya; Barun Ghosh; P K Datta; Sekhar C Ray; Sayan Bhattacharyya

doi:10.1039/c9sc01183h

All-inorganic quantum dot assisted enhanced charge extraction across the interfaces of bulk organo-halide perovskites for efficient and stable pin-hole free perovskite solar cells

Chem Sci. 2019 Aug 23;10(41):9530-9541. doi: 10.1039/c9sc01183h. eCollection 2019 Nov 7.

Affiliations

¹ Department of Chemical Sciences , Centre for Advanced Functional Materials , Indian Institute of Science Education and Research (IISER) Kolkata , Mohanpur 741246 , India . Email: sayanb@iiserkol.ac.in.
² Department of Electrical Engineering , Indian Institute of Technology (IIT) Kharagpur , Kharagpur - 721302 , India.
³ Department of Physics , Indian Institute of Technology (IIT) Kharagpur , Kharagpur - 721302 , India.
⁴ Department of Physics , CSET , University of South Africa , Private Bag X6, Florida, 1710, Science Campus, Christiaan de Wet and Pioneer Avenue, Florida Park , Johannesburg , South Africa.

Abstract

In spite of achieving high power conversion efficiency (PCE), organo-halide perovskites suffer from long term stability issues. Especially the grain boundaries of polycrystalline perovskite films are considered as giant trapping sites for photo-generated carriers and therefore play an important role in charge transportation dynamics. Surface engineering via grain boundary modification is the most promising way to resolve this issue. A unique antisolvent-cum-quantum dot (QD) assisted grain boundary modification approach has been employed for creating monolithically grained, pin-hole free perovskite films, wherein the choice of all-inorganic CsPbBr _x I_3-x (x = 1-2) QDs is significant. The grain boundary filling by QDs facilitates the formation of compact films with 1-2 μm perovskite grains as compared to 300-500 nm grains in the unmodified films. The solar cells fabricated by CsPbBr_1.5I_1.5 QD modification yield a PCE of ∼16.5% as compared to ∼13% for the unmodified devices. X-ray photoelectron spectral analyses reveal that the sharing of electrons between the PbI₆ ^- framework in the bulk perovskite and Br^- ions in CsPbBr_1.5I_1.5 QDs facilitates the charge transfer process while femtosecond transient absorption spectroscopy (fs-TAS) suggests quicker trap filling and enhanced charge carrier recombination lifetime. Considerable ambient stability up to ∼720 h with <20% PCE degradation firmly establishes the strategic QD modification of bulk perovskite films.