Thermal annealing of P3HT: PCBM blends for photovoltaic studies

Fatma Demir, Niko Van Den Brande, Sabine Bertho, Dirk Vanderzande, Jean Manca, Bruno Van Mele, Guy Van Assche

Research output: Chapter in Book/Report/Conference proceedingConference paper

Abstract

Post production annealing is an essential step for raising power conversion efficiency of bulk heterojunction solar cells [1]. Since defining appropriate annealing temperatures and times is vitally important, the isothermal crystallization of poly(3-hexyl thiophene) (P3HT) and [6,6]-phenyl C61 - butyric acid methyl ester (PCBM) blend is investigated by Rapid Heat-Cool Calorimetry (RHC), Fast Scanning Differential Chip Calorimetry (FSDCC), and AC Differential Chip Calorimetry (ACDCC).
RHC is a fast-scanning DSC technique developed by TA Instruments [2], having a 10 times smaller furnace heated by Infrared light and a sample size of about 50 to 500 µg. The RHC permits to heat at rates of up to 2000 K.min-1 and cool at 750 K.min-1 and 500 K.min-1 down to 60 °C and 0 °C.
FSDCC allows temperature control of the sample and determination of its heat capacity by employing cooling and heating rates from 50 to 1 MKs-1 [3]. Since it is also possible to control the cooling rate, studying the kinetics of extremely fast crystallization and reorganization processes in thin films of semi-crystalline polymers on heating becomes possible.
ACDCC is used to study the step in heat capacity at the glass transition in nanometer size thin films with samples masses below 1 ng in a broad temperature range [4]. The AC-chip calorimeter allows for the frequency dependent measurement of complex heat capacity in the frequency range of 1 Hz to 1 kHz with a scan rate from 1 K.min-1 to 5 K.min-1 This method is very suitable for the solar cell blends since the film thickness can be determined and applied as it is in the production line of photovoltaic devices.
The rate of crystallization during thermal annealing can be linked to the long-term stability of the blend morphology.
Original languageEnglish
Title of host publicationCentral and Eastern European Conference on Thermal Analysis and Calorimetry, 7-10 September 2011,Craiova Romania
PublisherCEEC-TAC
Publication statusPublished - 7 Sep 2011

Keywords

  • solar cell blends
  • AC Chip Calorimetry
  • Fast Scanning Chip Calorimetry

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