Open AccessReduced recombination through CZTS/CdS interface engineering in monograin layer solar cells
Author(s) -
Marit Kauk-Kuusik,
Kristi Timmo,
K. Muska,
Maris Pilvet,
J. Krustok,
Mati Danilson,
Valdek Mikli,
Raavo Josepson,
Michael Grossberg
Publication year - 2022
Publication title -
jphys energy
Language(s) - English
Resource type - Journals
ISSN - 2515-7655
DOI - 10.1088/2515-7655/ac618d
Subject(s) - czts , materials science , heterojunction , optoelectronics , kesterite , solar cell , annealing (glass) , energy conversion efficiency , layer (electronics) , nanotechnology , composite material
The power conversion efficiency of CZTS solar cells is still limited by deep defects, low minority carrier lifetime and high recombination rates at the CZTS/CdS interface. The objective of this study was to find an effective method to reduce interface recombination of CZTS monograin layer solar cells. Two-step heterojunction formation process was applied by controlling the intermixing of Cd and Cu in the CZTS/CdS interface, which resulted in improved device efficiency up to 11.7%. Surface analysis by X-ray photoelectron spectroscopy confirmed the Cd diffusion into surface of CZTS after CdS air-annealing by forming an ultra-thin Cu 2 Zn x Cd 1-x SnS 4 layer. Also, external quantum efficiency measurements showed that the absorption edge shifts to longer wavelengths with addition of Cd into CZTS surface layer. This surface modification and replacement of CdS:Cu buffer layer by fresh CdS greatly reduced the interface recombination and improved the junction quality, contributing to an enhancement of J SC ∼3 mA/cm 2 (from 20.5 to 23.6 mA/cm 2 ), and fill factor ~14% (from 59.4 to 67.7%). Serial resistance of the CZTS monograin layer solar cells was significantly reduced from 2.4 Ω cm 2 to 0.67 Ω cm 2 . To understand in more detail the electrical behavior of highest efficiency CZTS monograin layer solar cell, the temperature dependent current–voltage characteristics were analyzed.