Although individual commercial thermoelectric module has been widely investigated and its cooling behavior is clear, jointed thermoelectric modules show completely different cooling behavior and higher coefficient of performance (without the change of input electrical power) which requires further study. At the first step of this research, cooling characteristics of 2-jointed, 4-jointed and 6-jointed thermoelectric modules are experimentally evaluated and discussed under the same range of input electrical power. In the same total input electrical power, 6-jointed TEM (thermoelectric module) provided around 100% higher COP (coefficient of performance) than the 2-jointed TEM which was significant. Cooling behavior of different-number jointed TEM (in the same input power) are analyzed and discussed in this paper. In the second step of this research, the COP of 6-jointed TEM cooler (selected from the first step) has been increased again by proposition of two new techniques based on the modification of the popular rectangular-fin heat sink. Attempts are made to further enhance the COP of the system by two methods including "perforating technique" and "spring wire technique" through a Peltier air cooler which have not been proposed before. In the same electrical power input, perforating technique enhanced the thermal performance of the Peltier air cooler around 50% (totally 150% compared to the 2-jointed TEM with simple heat-sink) and the use of spring-wire between the fins of heat-sink improved the COP around 130% (totally 230% compared to the 2-jointed TEM with simple heat-sink). Exact explanation of the quality/quantity and improvement reasons of each technique are described in this paper for different working conditions of the cooler.