Low-Energy-Loss Polymer Solar Cells with 14.52% Efficiency Enabled by Wide-Band-Gap Copolymers

Abstract

SummaryTwo wide band-gap copolymers poly[4,8-bis(5-(2-butylhexylthio)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-TZNT] (PBDTS-TZNT) and poly[4,8-bis(4-fluoro-5-(2-butylhexylthio)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-TZNT] (PBDTSF-TZNT) based on naphtho[1,2-c:5,6-c]bis(2-octyl-[1,2,3]triazole) (TZNT) and benzo[1,2-b:4,5-b']dithiophene (BDT) with different conjugated side chains have been developed for efficient nonfullerene polymer solar cells (NF-PSCs). The rigid planar backbone of BDT and TZNT units imparted high crystallinity and good molecular stacking property to these copolymers. Using 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone)-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]-dithiophene (ITIC) as the acceptor, PBDTSF-TZNT devices showed a high Voc of 0.98 V with an Eloss of 0.61 eV. On selecting 3,9-bis(2-methylene-(5,6-difluoro-(3-(1,1-dicyanomethylene)-indanone)-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b’]-dithiophene (IT-4F) instead of ITIC, the devices maintained the high Voc of 0.93 V with an even lower Eloss of 0.59 eV. The combination of the above-mentioned low Eloss, broadened absorption, better matched energy level, improved crystallinity, and fine-tuned morphology promoted the power conversion efficiency (PCE) of PBDTSF-TZNT:IT-4F devices from 12.16% to 13.25%. Homo-tandem devices based on PBDTSF-TZNT:IT-4F subcells further enhanced the light-harvesting ability and boosted the PCE of 14.52%, which is the best value for homo-tandem NF-PSCs at present.

Single‐Junction Polymer Solar Cells with 16.35% Efficiency Enabled by a Platinum(II) Complexation Strategy

“…To get insight of the smaller E loss enabled by Pt‐complexation, the charge transfer state energy ( E CT ) and reorganization energy (λ) were estimated. E CT and λ of Pt0 and Pt10 devices were extracted from Equation according to Marcus theorywhere EQE PV is the photovoltaic EQE, f is proportional to the absorption strength of the charge transfer state and the density of the donor/acceptor interfaces, λ represents the reorganized energy of the charge transfer states, and E is the photon energy . As shown in Figure S5d (Supporting Information), the E CT was calculated to be 1.28 eV for Pt0 devices, corresponding to the E loss resulting from charge transfer ( E g − E CT ) of 0.05 eV.…”

Performance and Matching Band Structure Analysis of Tandem Organic Solar Cells Using Machine Learning Approaches

“…Recently, Peng and coworkers demonstrated a tandem OSC with a PCE of 14.52%. By designing the high‐performance TZNT‐based wide‐bandgap copolymers for the front cell, the V oc of the PBDTSF‐TZNT:IT‐4F‐based tandem OSCs reached 1.82 V; thus, the PCE of the tandem OSC achieved a value above 14% . This was a powerful demonstration that donor materials with a strong absorption should play a tremendously important role to realize high efficiency in tandem OSCs.…”

“…As a test of the ability of the Random Forest model to predict new tandem configurations (e.g., nonfullerene acceptor‐based tandem OSCs), IT‐4F and IT‐M acceptor‐based tandem OSCs were used to validate the model. Prediction errors relative to the experimental data were 7.9–9.2%, as shown in Table .…”

Photonic effect of a central ultrathin metal film on the performance of series and parallel homo-tandem solar cells

“…On the other hand, 2T cells are easier to manufacture than 3T, because they do not required to make an electrical connection to a central electrode. Moreover, they have been actively studied over the past decade [25,26,27,28,29,30,31,32] and they already show high efficiency, up to 14.52% [33] (the best demonstrated efficiency of hetero-tandem and 3T homo-tandem being 13-14% [4,34,35] and 11.08% [36], respectively) and can potentially show an open circuit voltage of up to 2.13 V [37].…”