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Manipulating Depletion Region of Aqueous‐Processed Nanocrystals Solar Cells with Widened Fermi Level Offset
Author(s) -
Wang Lijing,
Chen Nannan,
Jin Gan,
Feng Tanglue,
Du Xiaohang,
Liu Fangyuan,
Sun Henan,
Yang Bai,
Sun Haizhu
Publication year - 2018
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201803072
Subject(s) - materials science , energy conversion efficiency , aqueous solution , open circuit voltage , depletion region , short circuit , nanotechnology , nanocrystal , optoelectronics , photovoltaic system , solar cell , kesterite , chemical engineering , layer (electronics) , czts , voltage , chemistry , electrical engineering , engineering
Abstract Water soluble nanocrystals (NCs) are promising materials in aqueous‐processed solar cells because of their high extinction coefficient, low‐cost, and favorable photoelectric characteristics. However, the power conversion efficiency (PCE) of the present aqueous‐processed NC solar cells is restricted by the short depletion region of the active layer and limited Fermi level offset between NCs and the electron transport layer. Herein, these issues are effectively addressed by preparing Cd x Zn 1– x Te NCs capped with 2‐aminoethanethiol hydrochloride. The introduction of Zn 2+ into CdTe NCs widens the Fermi level offset from 0.68 to 0.74 eV, lengthens the depletion region from 130 to 137 nm, and hence brings obvious improvement in the open circuit voltage ( V oc ) and fill factor. Especially, the depletion region is successfully tuned from 137 to 171 nm, and even lengthened to a record thickness of 200 nm based on aqueous‐processed solar cells. As a result, a champion thickness ratio (74%) of depletion region to active layer (200/270 nm) is achieved. A champion PCE of 5.96% and short‐circuit current ( J sc ) of 21.2 mA cm −2 are achieved among aqueous‐processed NC solar cells. This work provides a simple way to prepare polynary NCs and highlights a prospective method to develop more efficient and cost‐effective solution‐processed environment friendly solar cells.