light sensing LEDs

Here is a simple circuit which I have tried and it works.

It is in the thumbnail at the end of this post.

D2 is actually the phototransistor which looks like a diode and, like a diode, works in only one direction.

The phototransistor I used was MT-P500M4D but I think almost any phototransistor will work, as will almost any npn transistor.
You can also add more LED's in series.
How the circuit works is that in the day when there is IR light around, the transistor conducts, and it is as if the - side of the battery were connected to the base of the npn transistor. Negative switches the transistor off.

In the dark, the phototransistor becomes an infinite resistance, so now the base is connected to the + side of the battery through the 1k resistor. Positive switches the npn on. Thus the transistor conducts, and the LED goes on.

 

Better use 555 which have enough current capacity to drive all the 10 LEDs. No other transistors needed. Use CMOS version to keep current low.