TY - JOUR
T1 - Precise Control of Phase Separation Enables 12% Efficiency in All Small Molecule Solar Cells
AU - Bin, Haijun
AU - Angunawela, Indunil
AU - Qiu, Beibei
AU - Colberts, Fallon J.M.
AU - Li, Mengmeng
AU - Dyson, Matthew J.
AU - Wienk, Martijn M.
AU - Ade, Harald
AU - Li, Yongfang
AU - Janssen, René A.J.
PY - 2020/9/1
Y1 - 2020/9/1
N2 - Compared to conjugated polymers, small-molecule organic semiconductors present negligible batch-to-batch variations, but presently provide comparatively low power conversion efficiencies (PCEs) in small-molecular organic solar cells (SM-OSCs), mainly due to suboptimal nanomorphology. Achieving precise control of the nanomorphology remains challenging. Here, two new small-molecular donors H13 and H14, created by fluorine and chlorine substitution of the original donor molecule H11, are presented that exhibit a similar or higher degree of crystallinity/aggregation and improved open-circuit voltage with IDIC-4F as acceptor. Due to kinetic and thermodynamic reasons, H13-based blend films possess relatively unfavorable molecular packing and morphology. In contrast, annealed H14-based blends exhibit favorable characteristics, i.e., the highest degree of aggregation with the smallest paracrystalline π–π distortions and a nanomorphology with relatively pure domains, all of which enable generating and collecting charges more efficiently. As a result, blends with H13 give a similar PCE (10.3%) as those made with H11 (10.4%), while annealed H14-based SM-OSCs have a significantly higher PCE (12.1%). Presently this represents the highest efficiency for SM-OSCs using IDIC-4F as acceptor. The results demonstrate that precise control of phase separation can be achieved by fine-tuning the molecular structure and film formation conditions, improving PCE and providing guidance for morphology design.
AB - Compared to conjugated polymers, small-molecule organic semiconductors present negligible batch-to-batch variations, but presently provide comparatively low power conversion efficiencies (PCEs) in small-molecular organic solar cells (SM-OSCs), mainly due to suboptimal nanomorphology. Achieving precise control of the nanomorphology remains challenging. Here, two new small-molecular donors H13 and H14, created by fluorine and chlorine substitution of the original donor molecule H11, are presented that exhibit a similar or higher degree of crystallinity/aggregation and improved open-circuit voltage with IDIC-4F as acceptor. Due to kinetic and thermodynamic reasons, H13-based blend films possess relatively unfavorable molecular packing and morphology. In contrast, annealed H14-based blends exhibit favorable characteristics, i.e., the highest degree of aggregation with the smallest paracrystalline π–π distortions and a nanomorphology with relatively pure domains, all of which enable generating and collecting charges more efficiently. As a result, blends with H13 give a similar PCE (10.3%) as those made with H11 (10.4%), while annealed H14-based SM-OSCs have a significantly higher PCE (12.1%). Presently this represents the highest efficiency for SM-OSCs using IDIC-4F as acceptor. The results demonstrate that precise control of phase separation can be achieved by fine-tuning the molecular structure and film formation conditions, improving PCE and providing guidance for morphology design.
KW - chlorination
KW - crystallization
KW - organic solar cells
KW - phase separation
KW - small molecular donors
UR - http://www.scopus.com/inward/record.url?scp=85088837487&partnerID=8YFLogxK
U2 - 10.1002/aenm.202001589
DO - 10.1002/aenm.202001589
M3 - Article
AN - SCOPUS:85088837487
VL - 10
JO - Advanced Energy Materials
JF - Advanced Energy Materials
SN - 1614-6832
IS - 34
M1 - 2001589
ER -