Over 12% Efficiency Nonfullerene All‐Small‐Molecule Organic Solar Cells with Sequentially Evolved Multilength Scale Morphologies

Abstract

mobility. [18] However, P-OSCs have a drawback in batch-to-batch reproducibility of donor polymers, which potentially limits the mass deployment of OSCs. [19] Compared to P-OSCs, small-molecule based OSCs (SM-OSCs) are more attractive in commercialization because of well-defined molecular structures, [20][21][22] simpler synthesis and purification, [23][24][25] and low batch-to-batch variations. [26][27][28][29] With the SM donors developed, the state-of-the-art SM-OSCs show similar PCEs as those obtained for P-OSCs (over 11%) using fullerene derivative, PCBM, as the electron acceptor. [19,[30][31][32][33] However, when the NFSM acceptors were used in nonfullerene-based small molecule organic solar cells (NFSM-OSCs) their PCE can only reach slightly over 10% [34][35][36][37] which is much lower than those obtained for nonfullerene polymer solar cells (NFP-OSCs) with usually PCE over 13%. [38,39] The progress of NFSM-OSCs is strongly lagged behind their polymer counterparts.The PCE of an OSC is determined by three parameters, opencircuit voltage (V oc ), short-circuit current density (J sc ), and fill factor (FF). The main reason for the low PCE in NFSM-OSCs is due to their relative low J sc and FF. [40,41] As shown in Table S1 (Supporting Information), all of the efficient NFP-OSCs with PCE over 14% show high J sc (>20 mA cm −2 ) and high FF In this paper, two near-infrared absorbing molecules are successfully incorporated into nonfullerene-based small-molecule organic solar cells (NFSM-OSCs) to achieve a very high power conversion efficiency (PCE) of 12.08%. This is achieved by tuning the sequentially evolved crystalline morphology through combined solvent additive and solvent vapor annealing, which mainly work on ZnP-TBO and 6TIC, respectively. It not only helps improve the crystallinity of the ZnP-TBO and 6TIC blend, but also forms multilength scale morphology to enhance charge mobility and charge extraction. Moreover, it simultaneously reduces the nongeminate recombination by effective charge delocalization. The resultant device performance shows remarkably enhanced fill factor and J sc . These result in a very respectable PCE, which is the highest among all NFSM-OSCs and all small-molecule binary solar cells reported so far.

Subtly adjusted active layer self‐assembly process for efficient organic solar cells

“…According to the corresponding EQE spectra, the integrated J sc values of the OSCs are 11.89, 12.60 or 12.93 mA cm −2 for the active layer without treatment and with TA or TA&SVA treatment, respectively. The integrated J sc values are slightly smaller than the corresponding measured value with about 3% deviation; a similar phenomenon is commonly reported in other published papers . To further investigate the post annealing treatment and performance improvement of the OSCs, the shunt resistance ( R sh ) and series resistance ( R s ) were calculated according to the J–V curves of the OSCs in the dark .…”

“…Small molecule based OSCs show better advantages in commercialization due to high repeatability from batch to batch and easy purification of materials . So far, the power conversion efficiency (PCE) of small molecule OSCs has reached ca 12% . One vital condition for high PCEs is the well optimized electron donor/acceptor (D/A) phase separation of the active layers, namely sufficiently connected D/A domains with proper domain size .…”

“…5,6 So far, the power conversion efficiency (PCE) of small molecule OSCs has reached ca 12%. 7,8 One vital condition for high PCEs is the well optimized electron donor/acceptor (D/A) phase separation of the active layers, namely sufficiently connected D/A domains with proper domain size. 9,10 Sun et al have reported that the PCE of OSCs was increased from 5.2% to 9.3% by optimizing the D/A phase separation of benzodithiophene terthiophene rhodanine (BTR):PC 71 BM active layers by tetrahydrofuran solvent vapor annealing (SVA) treatment.…”

New Conjugated Polymers Based on Dithieno[2,3‐e:3′,2′‐g]Isoindole‐7,9(8H)‐Dione Derivatives for Applications in Nonfullerene Polymer Solar Cells

“…However, the phase separation in the range of the exciton diffusion length (≈20 nm) is beneficial for both exciton dissociation and charge transfer. These results indicate that the fluorination of the backbone of the polymer improves the crystallinity and planarity and the phase separation in the active layer.…”

As‐Cast Ternary Organic Solar Cells Based on an Asymmetric Side‐Chains Featured Acceptor with Reduced Voltage Loss and 14.0% Efficiency

“…In addition to the innovation of active materials development, device optimization processes including solvent additives, interfacial engineering, and ternary strategies, also play critical roles in improving the performance of solar cells. Among these, constructing ternary solar cells, which have two donor materials paired with one acceptor (2D/1A) or one donor paired with two acceptors (1D/2A), is a simple and effective way to improve the overall device performance .…”