OAIID:oai:osos.snu.ac.kr:snu2013-01/104/0000001236/8SEQ:8PERF_CD:SNU2013-01EVAL_ITEM_CD:104USER_ID:0000001236ADJUST_YN:NEMP_ID:A004558DEPT_CD:445CITE_RATE:0FILENAME:이종원.pdfDEPT_NM:재료공학부EMAIL:whjpoly@snu.ac.krCONFIRM:

Choi, Yoon Suk

Jo, Won Ho

Lee, Jong Won

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Simple Structured DPP-based  Small Molecules for  High Efficient Organic Photovoltaics Jong Won Lee, Yoon Suk Choi, Won Ho Jo* Department of Materials Science and Engineering, Seoul National University, Seoul 151-742, Korea  Synthesis  Results Introduction  Photovoltaic properties Conclusions  TDPP-based Small molecules (TDPP)2, T(TDPP)2 and Ph(TDPP)2 are successfully synthesized and show VOC of 0.84 V, 0.80 V and 0.93 V, respectively. Objectives  To synthesize low bandgap small molecules (SM) based on thiophene-capped diketopyrrolopyrrole (TDPP) unit and different electron-donating group with thiophene (T) or phenylene (Ph)  To precisely control the HOMO energy level by introducing T or Ph  To investigate the optical, electrochemical, and photovoltaic properties of the SMs  Ph(TDPP)2 shows the best PCE of 4.01 % with a high VOC of 0.93 V and a high JSC of 9.09 mA/cm2.  Morphology study SMs SM:PC71BM  (w/w) VOC (V) JSC (mA/cm2) FF PCE  (%) SM1 1:1 0.85 5.41 0.34 1.59 SM2 1:1 0.77 3.60 0.89 0.89 SM3 1.25:1 0.92 8.36 0.45 3.47 Small molecule λmax, CHCl3 (nm) λmax, film  (nm) Egopt  (eV) HOMO  (eV) LUMO (eV)a SM1 625 628 1.51 -5.18 -3.66 SM2 615 638 1.51 -5.17 -3.68 SM3 601 612 1.66 -5.31 -3.65  Optical and electrochemical properties SMs SM:PC71BM  (w/w) VOC (V) JSC (mA/cm2) FF PCE  (%) SM1 1:1 0.84 7.40 0.37 2.31 SM2 1:1 0.80 4.30 0.43 1.49 SM3 1.25:1 0.93 9.09 0.47 4.01  Structure study  Weak electron-donating power of Ph → Deep HOMO energy level and large bandgap of SM1  Same electron-deficient unit → almost the same LUMO energy levels of SMs As-cast SM1:PC71BM (1:1 w/w) SM2:PC71BM (1:1 w/w) SM3:PC71BM (1.25:1 w/w) Homogeneous one-phase morphology Macro-phase separated morphology  Bicontinuous two-phase nanostructured morphology  The length scale of phase separation   (a): exciton recombination before reaching the D/A interface  (b): blocking of efficient charge transport   (c): optimum for charge separation and transport  Bandgap tuning in D-A type small molecule   Intramolecular charge transfer Donor Acceptor Low Bandgap LUMO HOMO LUMO HOMO LUMO HOMO Donor (D) : electron-rich unit Acceptor (A) : electron-deficient unit A D A Weak electron-donating power of donor → Deep HOMO energy of small molecule → high VOC  VOC ∝ HOMO Energy level of small molecules aCalculated from LUMO = HOMO + Egopt  Strong X-ray diffraction peak at 2q  = 6.10° for all SMs → (100) diffraction with 14.4 Å  interlayer spacing  The highest crystallinity of SM1 from XRD (a) and DSC (b, c) data SMs SM:PC71BM  (w/w) h (cm2/V s) e (cm2/V s) SM1 1:1 6.010-5 2.210-4 SM2 1:1 2.510-5 2.010-4 SM3 1.25:1 8.810-5 2.410-4  Nano-scale phase separation of SM3              → high hole mobility → high JSC   h e  Charge carrier mobility of SMs (SCLC)   After annealing  As-cast  After annealing at 120 °C for 10 min. In CHCl3 In film 

Simple Structured DPP-based Small Molecules for High Efficient Organic Photovoltaics

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Simple Structured DPP-based Small Molecules for High Efficient Organic Photovoltaics

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