Modulation of Alkyl Chain Length on the Thiazole Side Group Enables Over 17% Efficiency in All‐Small‐Molecule Organic Solar Cells

Abstract

Molecular innovation is highly desirable to achieve efficient all‐small‐molecule organic solar cells (SM‐OSCs). Herein, three small‐molecule donors (SMDs) with alkylated thiazole side groups (namely BO‐1, HD‐1, and OD‐1), which differ only in the alkyl side chain are reported. Although these SMDs possess similar absorption profiles and molecular energy levels, their crystallinity and miscibility with BTP‐eC9 slightly decrease along with the elongation of the alkyl side chain. After blending with BTP‐eC9, different miscibility leads to different degrees of phase separation. Among these SM‐OSCs, the HD‐1‐based device shows a decent bulk‐heterojunction (BHJ) morphology with proper phase separation and more dynamic carrier behavior. Thus, compared to the BO‐1 and OD‐1‐based devices, the HD‐1‐based device achieves a higher short‐circuit current of 26.04 mA cm−2 and a fill factor of 78.46%, leading to an outstanding PCE of 17.19%, which is one of the highest values among SM‐OSCs. This work provides a rational design strategy of SMDs for highly efficient SM‐OSCs.

Regulating the reorganization energy and crystal packing of small-molecule donors enables the high performance of binary all-small-molecule organic solar cells with a slow film growth rate

“…2f and Table S8, ESI†). 25,29 This result indicates that the T27 -based device exhibits good tolerance to film thickness and is suitable for roll-to-roll fabrication.…”

“…[20][21][22][23][24][25] With recent innovation of device-processing engineering and photovoltaic materials, particularly the development of Y-series acceptors, the power conversion efficiencies (PCEs) of the ASM-OSCs have surpassed 16%. [26][27][28][29][30] However, the PCEs of the ASM-OSCs still lag behind those of the polymer-based OSCs. 31,32 Therefore, engineering high-performance small molecule donors (SMDs) is crucial for enhancing the PCEs of the ASM-OSCs.…”

Progress and Future Potential of All-Small-Molecule Organic Solar Cells Based on the Benzodithiophene Donor Material

“…The length of alkyl side chain significantly influences the crystallinity and blend morphology of the active layer. Owing to decent BHJ morphology, the HD-1 based molecule achieved a champion device efficiency of 17.19% with the BTP-eC9 acceptor, which is currently one of the highest PCEs among SM-OSCs [ 52 ].…”

Recent Advances in Organic Photovoltaic Materials Based on Thiazole‐Containing Heterocycles

“…On the basis of this, next year they modified the alkyl side chain length of Tz and synthesized three small molecule materials, BO‐1, HD‐1, and OD‐1. [ 19 ] The device based on HD‐1 achieved the highest PCE of 17.19% and J SC of 26.04 mA cm −2 due to the more favorable phase separation.…”

“…Until the present moment, Tz‐based photovoltaic materials as donors or acceptors have been widely reported and yielded high performance, such as PBTTz3Cl, [ 18 ] HD‐1. [ 19 ] In 2012, Zhan et al reviewed the developments in Tz‐based small molecules and polymers for applications in OSCs. [ 20 ] As the research progressed, a series of the building blocks derived from Tz have also been developed, as shown in Figure , including thiazolo[5,4‐d]thiazole (TzTz), benzo[d]thiazole (BTz), benzo[1,2‐d:4,5‐d’]bis(thiazole) (BBTz), thieno[3,4‐d]thiazole (TTz), dithieno[3“,2”:3,4;2“”,3“”:5,6]benzo[1,2‐d]thiazole (DTBTz), thiazolo[4“,5”:4,5]benzo[1,2‐c][1,2,5]thiadiazole (TzBT), dithiazolo[4,5‐b:4“,5”‐e]pyrazine (PDTz), and so on.…”